Double Attack?

Does anyone know if it is possible to have a unit attack twice, without cooldown then has his cooldown? For example, he fires 2 projectiles then cooldowns. Think of the SC Valkerie and her attack. Also, if the first attack kills the target, I want him to cooldown before attacking again.

I think you could trigger it with a dummy unit that has as much damage as the you want to attack twice and triggers, something like:
Event - Unit is attacked
Condition - Unit-type of attacking unit equal to (unit which shoots twice)
Action - Create 1 (dummy attacker unit) at position of attacking unit
Order last created unit to attack once attacked unit
Add a generic expiration timer 2 seconds to last created unit

It wont work for a melee attacker cause I want the 2 attacking animations.

i dont think its really possible, except maybe with a trigger the causes the unit to play its attack animation the secodn time and have an invisable unit with the same dmg stats attack the target via an order trigger.

Have a dummy ability... Does nothing, just gives info.

Have a trigger calculate the random "double attack"

When it hits the point where it "double attacks", have the trigger add the ability Barrage. When he begins attacking a unit again, remove the ability barrage.

Customize the ability Barrage to only hit 2 units.

MysticGeneral: Won't that give the attacking unit a chance to attack 2 nearby units once instead of 1 unit twice?

Isn't that what he wanted?...?

If you ever played Seiken-Densetsu it's like Kevin and Hawk's attack.
Basically I want the unit to slash 2 times with attack animation then a long cooldown. Not 2 diff units but the same one. If the first slash kills the unit he has the long coolsdown.
And its not an ability.

Just increase the animation speeds for like 1 second and allow him to hit 2 times then bring him back to normal... ><.